Temporal change of train noise in underground stations
Ryota Shimokura , Yoshiharu Soeta

A covered underground station is a reverberant sound field. The acoustical characteristics of train noise in the station are determined by the noise source as well as the sound field. In a previous study, the A-weighted equivalent continuous sound pressure level (LAeq) of train noise in the island platform was higher than that in the side platform. The LAeq was the averaged value in the long duration (10 to 30 s). However, the acoustical characteristics of train noise changes dynamically in the duration, and the temporal change affects the comfort of passengers. The aim of this study
was to evaluate the temporal change of train noise in underground stations. The train noise in underground stations (side and island platforms) were measured in five different lines (a total of 10 stations), and the increment and decrement of the LAeq were calculated when the train came into and left the station. The change of sound quality was evaluated by the standard deviation of the autocorrelation function (ACF) and interaural cross-correlation function (IACF) parameters (τ1, φ1, and IACC). The effect of the lines on the changes was significant, but the effect of the platform
types was not significant. Since each line has a different train car, the changes in train noise were dependent mainly on the train cars (i.e. sound sources), not on the platform types (i.e. sound fields).

Key words: underground station, train noise, train car, side platform, island platform